Investigations on the reactions of acetoxy allenoates and indolyliodoarylsulfonamides in cyclization of C C bond formation

Abstract

xiv newlineSynopsis newlineThis thesis is divided into two parts: Part-A and Part-B. Part-A deals with the following newlinetopics: (i) Pyridine vs DABCO vs TBAB in annulation of and#948;-acetoxy allenoates with thioamides newlineleading to dihydrothiophene, thiopyran, and thiazole scaffolds, (ii) DBU-catalyzed ringexpansion newlineor ene-amine formation involving and#948;-acetoxy allenoates and N-sulfonyl hydrazides (iii) newlineDMAP and DBU-catalyzed annulation of and#948;-acetoxy allenoates with 1,3-dicarbonyl compounds newlineleading to dihydropyrans and 4H-pyrans. Part-B deals with the palladium-catalyzed newlineintramolecular transformations of indolyl-iodoarylsulfonamides that lead to ortho-sulfonamidobi( newlinehetero)aryls via C2-arylation or polycyclic sultams via C3 arylation. newlineCompounds synthesized in the present study are, in general, characterized by melting newlinepoint, IR, and NMR [1H, 13C{1H} and 19F] techniques in conjunction with LC-MS/ HRMS/ newlineelemental (CHN) analyses. X-ray structure determination has been undertaken wherever newlinerequired. A summary and, as well as references, are given at the end of each part. newlinePART A newlineIn Chapter 1, a review of the literature on aspects relevant to this part is presented. In newlineChapter 2, the results obtained are discussed while in Chapter 3, the experimental details are newlinedescribed. The precursors used in the present study are shown in Chart 1. The compound newlinenumbers given here are different from that in the main part of the thesis. newlineChart 1. Precursors used in the present study (Part A) newlinexv newline(i) Reaction of and#948;-acetoxy allenoates with thioamides: Pyridine-catalyzed (3 + 2) annulation newlineleading to dihydrothiophene motifs and synthetic utility newlineIn the present work, we wanted to explore the reactivity of and#948;-acetoxy allenoates with newlinethioamides under Lewis base catalysis. Thus pyridine catalyzed (3+2) annulation offered newlinedihydrothiophene motifs 6 with excellent stereoselectivity (Scheme 1). Here, and#948;-acetoxy allenoate newlinefunctions as a 2C synthon. Upon treatment with DDQ, 6aj could be oxidized to thiophene 7aj in newline51% yield. Mechanistic details are discussed in a later section. newlineSch